1. Field of the Invention
The invention relates to a device with an acoustic guard protecting a microphone module from reflected sound waves.
2. Description of the Related Art
A microphone module can be mounted in a rearview mirror or global positioning system (GPS) receiver in a car for the driver or passengers to communicate. As shown in FIGS. 1A and 1B, for example, a unidirectional microphone 16 is mounted in a GPS receiver 14 to receive sound via two acoustic openings 161 and 162. The unidirectional microphone 16 is provided to clearly receive sound from the driver (or passengers) in front of the GPS receiver 14 and avoid environmental noise. Directivity of the unidirectional microphone 16 (sensitivity of a microphone more in one direction than another), however, is deteriorated or even cancelled.